Spark plug fouling and pre-ignition caused by hot spark plugs is a significant issue in areas with poor fuel quality control. Fuel additives such as MMT or ferrocene may build up electrically conductive and thermally insulating deposits on the spark plug ceramic. Such build up may cause misfires or pre-ignition (PI). Due to the potential severity of misfires or PI at high speed and load in boosted engines, vehicle manufacturers may recommend very short spark plug change intervals. However, as the issue of misfires and PI due to fuel additive build up is often a geographically and seasonally limited issue, such frequent spark plug changes may be unnecessary for some vehicles. One approach to detecting spark plug fouling includes performing ion detection to measure ionization current generated from combustion through spark plug electrodes. However, ion detection involves the addition of specialized hardware elements within a typical ignition system, thereby increasing the cost and complexity of the system.
The inventors have recognized the above issues, and offer a system to at least partly address said issues. In particular, the present disclosure provides low cost and easy-to-implement methods and systems for continuously detecting the fouling level present at the spark plug, such that the customer may only be warned to change plugs when conditions warrant. Under some conditions, the methods and systems of the present disclosure may also help to reduce spark plug fouling, thereby offering further extensions of the time between spark plug changes. In one example, a method to address the above-described issues includes performing a high-frequency restrike and determining a spark plug condition based on a determination of coil primary current during the restrike. In this way, spark plug fouling may be detected by evaluating the primary current in the ignition system without using additional specialized hardware.
The present disclosure may offer several advantages. For example, by providing spark plug change recommendations based on evidence of malfunction or degradation, rather than a predetermined period of time or amount of vehicle usage, such recommendations may ensure that spark plug change recommendations are provided in a timely manner. The recommendations supported by measured indications of spark plug fouling may ensure that spark plug change recommendations are not provided too soon, resulting in increased cost for the driver, or too late, resulting in damage to the vehicle. Further, by determining spark plug fouling based on primary current in the ignition system, the overall cost of the ignition system may be reduced relative to systems that utilize other spark plug fouling determination mechanisms, such as ion detection, by controlling existing hardware elements.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.